Morrison, CO 80453 Frost Dates
Morrison, CO: when does the frost end?
Around 05/23 is the usual last spring frost, about 268 days away. Fall's first freeze usually shows up around 09/22, roughly 118 days after the last spring frost.
Morrison sits in USDA Zone 5b (-15 to -10°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
With roughly 4 weeks until Morrison's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/23 isn't a guarantee
05/23 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/09 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/10 and only about 1 year in 10 sees frost after that.
Morrison against the rest of the dataset
At roughly 118 frost-free days, Morrison places 39,229 of 40,283 ZIP codes in this dataset. Within CO, it ranks 472 of 624.
Learn more
Before leaning on 80453's figures: local microclimates explains what one yard in Morrison can differ from the 80453 normal, while zone vs. frost date explains why Zone 5b and Morrison's frost date answer different questions.